Participants sit inside the structure where it is soft and white and a bit like a cocoon. Designed by Arup, it is very very quiet, given the traffic and tourists flooding the square outside. The creators say that "One of the challenges that the Portal has set itself is how to change our experience of urban space".

The sound does surround you and make you want to stay awhile. Or is that just the exhaustion from running around the London Design Festival all day?

After the Festival, it is going to an art college where it will be part of an inter-college project to explore the dimensions of sound. The BE OPEN Foundation will commission new sound works from the students and these will be heard in the spring.